Electromagnetic and absorption properties of nano-sized and micro-sized Fe4N particles

Abstract

Single-phase Fe4N has been synthesized by gaseous nitriding micro-sized and nano-sized Fe particles at 793 K under ammonia atmosphere. The electromagnetic properties of their wax composite with 75 wt.% magnetic particles have been investigated within the frequency range of 1–18 GHz. Both size and phase effects on the microwave absorption properties were discussed on the results of scanning electronic microscopy, X-ray diffraction, hysteresis loop, and the frequency dependence of complex permittivity and permeability. The results show that nano-sized particles have superior absorbing performance at lower frequency band than the corresponding micro-sized ones, which is mainly attributed to the higher dielectric constant caused by interfacial polarization. The Fe4N composites exhibit much stronger absorption in 2–8 GHz than Fe composites. The reflection loss (RL) values of less than −10 dB are observed in a wide frequency bandwidth from 1.8 to 11 GHz for nano-sized Fe4N composite with absorber thickness of 1.2–5.0 mm. Its minimum RL value (RLmin = −33 dB) appears at 3.5 GHz with a thickness of 3.0 mm. This study demonstrates the possible application of producing thin and light absorbers from nano-sized Fe4N particles for microwave absorption at S and C bands (2–8 GHz).